Safety switch-box



'Huf WW" E. M. COFFIN.

SAFETY SWITCH BOX. APPLICATION FILED FEB. 25, 1918.

Patented Dec. 7, 1920.-

UNITED STATES PATENT OFFICE.

EVERETT M. COFFIN, 0F PIEDMONT, CALIFORNIA.

SAFETY SWITCH-BOX.

Specification of Letters Patent.

Patented Dec. '7, 1920.

Application filed February 25, 1918. Serial No. 218,926.

To all whom it may concern:

Be it known that I, EVERETT M. COFFIN, a citizen of the United States,residing at Piedmont, in the county of Alameda and State of California,have invented new and useful Improvements in Safety Switcha horizontalsection thereof on the line 2 2 of Fig. 1; Fig. 3 is a vertical sectionon the line 33 of Fig. 1 looking in the direction of the arrow; Fig. 4:is a similar section on the line 4l4l of Fig. 1.

Referring to the drawing, 1 indicates a knife switch mounted upon aninsulating base 2 and inclosed in a box-like receptacle 3. Said switchis operated by means of a link 4: secured at one end to the insulatingyoke 6 of the switch and at the other end to a U-crank arm 7 havingbearings in the sides of the receptacle and extended through one of saidsides to form a crank handle 8 by which the crank arm can be turned inits hearings to open and close the switch, so that it is not necessaryfor this purpose to open the receptacle. The lid 9 of the receptacle ishinged to one side thereof, as shown at 11, and has a knob or handle 12for opening and closing it. It is provided with a keeper 13 extendinginwardly from the lid, about opposite to said knob, which is engaged bya spring-actuated latch 14 pivoted on the adjacent side of the recep,

tacle and the movement of which is limited,

by the guide 25, said keeper having two notches 16 either of which canbe engaged by said latch. Secured to the inner side of said lid, nearits hinged edge, is a stop plate 17 which extends from said lid in aplane transverse to the line of the hinges and in the form of a sectorof a circle somewhat greater than a quadrant. This stop plate can movethrough an open-ended slot or recess 15 extending inwardly from the freeedge of the side of the receptacle to which the lid is hinged. Thestopplate extends from said lid in such a direction that, when the lid isdown, or, in other words when the receptacle is closed, the crank arm 7can just pass the edge 30 of the stop plate 17, but, if the lid israised to any extent, the stop plate swings into a position such thatsaid edge 30 advances into the path of the crank arm 7 tending to closethe switch, and prevent the same from being closed.

In Fig. 4 thelid is shown as closed and i one of the notches 16 engagedby the latch 14-. The other notch 16 is engaged by the latch 14 when thelid is not quite closed, but is closed sufiiciently to permit the arm 7topass the stop plate 17. But for the provision of this second notch theobject of the invention might be defeated by the 0perator nearly, butnot quite, closing the box and then closing the switch, in which caseaccess could be had to the closed switch by merely raisin the lid of thebox, said lid not then being locked. 7

Attached to said latch 14: is a finger 18, which is engaged by the arm 7only when the switch 1 is fully opened, thereby withdrawing the latch 14and allowing the lid 9 to be raised. I

It will be seen that, with the above described construction, the switchbox cannot be opened until. the switch is opened wide and the switchcannot be fully opened unless the switch box is fully closed. I

I claim:

In a safety switch box, the combination with a knife switch, of abox-like receptacle for containing the same, a crank arm operativelyconnected to said switch and having an operating handle extendingoutside the box, a pivoted lidfor closing the box, a'keeper secured tothe lid, a latch engaging said keeper for retaining the lid in a closedposition, means moving with the crank arm for withdrawing said latchfrom its operative position when the switch is opened, and'a stopcarried by the lid'and obstructing the movement of the crank arm exceptwhen the lid is closed sufficiently to

